Time and space are one thing. Time lacks a preferred moment in the exact same way that space lacks a preferred location.

I’ll have to ponder that a bit. My initial reaction is to wonder if it is just space that in influenced by relative motion, gravity etc. and that time – our measuring “instrument” – has to adjust to accommodate that change.

If there were no calipers, that mm would have no meaning.If there were no objects, distance would have no meaning.If there were no change, time would have no meaning.

Distance is the separation of points, not objects. Time is the separation of events.

It is arguably the case that if individual words have no meaning, their combination is also meaningless, but that is fatuous philology or, even worse, philosophy. Unlike philosophy, physical masturbation is at least pleasurable.

I'll take a short break from more pleasurable activities to explain that "London" and "Cambridge" are fuzzy patches on a map. Points within "London" and "Cambridge" are separated by all sorts of distances, mostly between 40 and 70 miles.You can define points within those fuzzy boundaries that are not associated with any particular object. In the absence of other data those points are conventionally located within Charing Cross and Great St Mary's respectively but if you want to navigate by dead reckoning from Cambridge airport to London City you will need to choose two other points.

And the pedantry prize is awarded to the old fool who pointed out that the change from boyhood to manhood is not an event, nor two events, but it may be denoted by a single event, arbitrarily chosen at 13, 16, 18 or 21 years after birth

Just like a millimeter is the gap between the jaws of a caliper gauge.

How small does something have to be to be a point rather than an object?

Small enough to be mathematically treated as one for the task at hand.

The lightning strikes in Einstein's train/platform thought experiment needed to be pretty precise and those events were as concise as Einstein could describe them. But on the other hand, other events like the Chicago fire are quite large because they usually are not compared with more precise things.

A point is not a "something". It is by definition infinitesimal, and therefore smaller than any "thing".

Infinitesimal is by definition: “an indefinitely small quantity; a value approaching zero.” My thinking is that if it is a quantity, and not zero, it must be something, but I am neither a mathematician or a physicist.

Experience teaches that trying to forge any kind of link between this sort of mathematical concept and the “real world” leads nowhere. Possibly a “put-down” type answer like:

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A point on a line has no length. A point on a timeline has no duration. What's the problem?

Where does it go from there? Perhaps try saying what the “problem” is. It’s always good to answer a question.

Quote from: Bill

I have no problem with either of those, in principle. However, in practice, can you show me a point that has no length, but is still there?

Similarly, a point on a timeline that is defined as having no duration may be theoretically valuable, but both the timeline, and the point are mathematical tools. What would be a physical example?

No reply. This is not an isolated example; which makes me wonder if I am asking a pointless question?

guest4091

One can argue that time exists if it is something that can be measured.

It's motion that is measured and labeled as 'time'. From early history: astronomical bodies in motion, to today's quantity of light waves.[/quote]

Perhaps you can suggest nonexistent things that nevertheless are measured. [/quote]

Time.

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Einstein allowed the definition of the time of event E to be relative to any frame of choice.

Yes he did, but the clock was 'local' from the point of observation, which becomes the basis for coordinate transformations..A. Einstein, 1905 paper, par.1:"It might appear possible to overcome all the difficulties attending the definition of ``time'' by substituting ``the position of the small hand of my watch'' for ``time.'' And in fact such a definition is satisfactory when we are concerned with defining a time exclusively for the place where the watch is located; but it is no longer satisfactory when we have to connect in time series of events occurring at different places, or--what comes to the same thing--to evaluate the times of events occurring at places remote from the watch."

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Of course it is perfectly legit to say that all observations are caused by past events, and causes are necessarily somewhere within the past light cone of observation event b.

That's essentially what I meant. All your observations are 'now'. The fossil is also in its current/now state. Observing an image of a nova, the star is in an historical state. The difference is between a and b.Thanks for the conversation.

Logged

guest4091

My sticking point was that Phyti seemed to find a few milliseconds without time.

Medical research in the past three decades has revealed the brain has multiple processes periodic and not, that serve as clocks, for most of the biological functions. There is an overall lag between sensory input and the consciousness of events. There is a mind-time connection. Comatose patients, amnesia, brain damage, etc, all interfere with ability to correctly sense intervals of time, short or long.

Experience teaches that trying to forge any kind of link between this sort of mathematical concept and the “real world” leads nowhere.

Far from it. A rigorous treatment of infintesimals leads to differential calculus, whence we get the whole world of classical physics, mesoscopic engineering and just about everything that distinguishes enlightened men from priests, politicians, philosophers and all the other human dross we scientists scrape off our shoes.

7:15 AM, GMT is a physical point in time. It isn't an event, since the location of where it is 7:15 is not specified and hardly unambiguous.

Thank you, you make one of my points more eloquently than I. 7:15 AM, GMT is a concept that, as far as I am aware, exists only in the minds of rational beings (apparently not universally); it is an invented “point” on an imaginary line that, conveniently, charts progress of/through time. Time, itself, as we have been discussing, is somewhat ethereal. It’s a relatively simple matter to propose a point of zero dimensions in such a scenario.

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A physical event is something like 2 billiard balls hitting, which yes, is a process, but one can narrow it to a point by specifying say the point of maximum force between the two objects.

This is probably the nearest anyone has come to identifying a physical point of zero dimensions. Unfortunately, the point of maximum force between the two objects has no independent existence, so could hardly qualify as a physical object.

Some good facts about time. They are what we can say about time in nature. I don't think anyone knows what time is.

Oh come now! A cow is a bovine quadruped that moos and poos, with milk in the middle. Time is what separates sequential events. These are definitions. Only a philosopher would pretend not to know what a cow "is". Farmers and scientists have more important things to think about, because we work with animals and time.

A rigorous treatment of infintesimals leads to differential calculus, whence we get the whole world of classical physics, mesoscopic engineering and just about everything that distinguishes enlightened men from priests, politicians, philosophers and all the other human dross we scrape off our shoes.

The original question remains unanswered. Perhaps the cognoscenti believe they can blind with science/maths this “human dross” before superciliously scraping them from their shoes.

Your post seems to say more about your personal prejudices than about the subject of the thread, but the former is something from which I would prefer to remain detached.

At some point, I think, I hijacked this thread. I don’t feel guilty about it because it has been a fruitful discussion, at least until recently. I’ve gained a lot from it, and would like to thank those who have coped patiently with my persistence. Unfortunately, the thread is showing signs of the sort of degeneration that one does not expect of TNS, so I am opting out.

I’m pulling together some thoughts, which will undoubtedly raise even more questions/objections. I’ll probably post these in a new thread, rather than stay with this one.

7:15 AM, GMT is a concept that, as far as I am aware, exists only in the minds of rational beings (apparently not universally); it is an invented “point” on an imaginary line that, conveniently, charts progress of/through time.

I'd hesitate to call it a line. 7:15 happens at every point in space. Different frames make it happen at different events, but there's damn few points in space where 7:15 doesn't happen at all.

The line could be your worldline, with a watch strapped to you defining 7:15. That worldline is not at all imaginary because it is completely occupied by you, as is nowhere else. That line (in particular the orientation of it at 7:15) defines 7:15 everywhere else at that event.

Quote from: Halc

A physical event is something like 2 billiard balls hitting, which yes, is a process, but one can narrow it to a point by specifying say the point of maximum force between the two objects.

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This is probably the nearest anyone has come to identifying a physical point of zero dimensions. Unfortunately, the point of maximum force between the two objects has no independent existence, so could hardly qualify as a physical object.

Well I never suggested a point was physical object. Heck, even physical objects are not physical objects when you get right down and dirty. The event I described with the billiard balls has a nice defined location and time, so it seems to suffice. But I agree, it isn't an object at all.